1. Field of the Invention
The present invention relates to a video camera and a video signal reproducing apparatus, each having a hand shake correcting function.
2. Description of the Related Art
In recent years, in association with the miniaturization and light weight of video cameras, a problem of hand shake has come to easily occur. Therefore, a video camera having a hand shake correcting function has been put into practical use.
As a hand shake correcting method of such a video camera, there has been known a method whereby a shake of the camera is detected by an angular velocity sensor and a cut-out position in an image memory is shifted in accordance with an output of the angular velocity sensor.
In such a hand shake correcting method of the video camera, the output of the angular velocity sensor is integrated by a low pass filter, and is converted from an angular velocity into an angle, thereby obtaining a correction amount. On the basis of the correction amount, an image plane is shifted. A limiter to set a correction limit value of an output of the low pass filter is provided so that the correction amount does not exceed the limit value.
The video camera having the image memory can enlargedly interpolate the image plane stored in the image memory. Such a function is called an electronic zoom. On the other hand, a zoom in which a zoom lens is moved is called an optical zoom.
In case of the hand shake correcting method such that a movement of the camera is detected by the angular velocity sensor and the correction is performed in accordance with the cut-out position in the image memory (for example, European Patent Application Publication No. 0498730), the shake of the image plane enhances with an increase in zoom magnification in the optical zoom region. It is, therefore, necessary to increase the correction amount in proportion to the zoom magnification.
On the other hand, in an electronic zoom region, it is sufficient to set the correction gain constant. This is because in the electronic zoom region, for example, in case of the electronic zoom of the double magnification, when there is a hand shake of (n) lines, the reading position in the image memory is shifted by (n) lines. Then, the content of the image memory is interpolated by two times and is read out. When the image data is shifted by (n) lines and is interpolated by two times and is read out, the correction of (2n) lines is executed.
Such a hand shake correcting apparatus has a low pass filter to convert from an angular velocity based on the shake of the camera detected by the angular velocity sensor into an angle. Since it is sufficient that the correction gain is constant in the electronic zoom region, hitherto, the gain of the low pass filter is set to the same as that in the control in the telescopic end of the zoom lens in the electronic zoom region.
However, when such a hand shake correcting function is added, a problem such that an image pickup plane becomes unnatural upon panning photographing has conventionally occurred. Namely, upon panning photographing, the camera is suddenly moved at the start of the panning. Due to this, the integration value of the angular velocity sensor rapidly increases and suddenly the value exceeds the correction limit. Accordingly, the image pickup plane becomes unnatural.
Namely, when the panning photographing is executed, a detection signal is outputted from the angular velocity sensor as shown in FIG. 13A. The detection signal is integrated by a low pass filter. The integration value reaches a correction limit LMT at a time point t.sub.11 as shown in FIG. 13B. Hitherto, as shown in FIG. 13C, the integration value is suddenly limited from a point P11 at the time point t.sub.11 at which the integration value reaches the correction limit LMT.
On the other hand, when the electronic zoom magnification rises, the portion which is not read out from the image memory is widened, so that the hand shake correction ability inherently increases. However, conventionally, the low pass filter which integrates the output of the angular velocity sensor is controlled in a manner similar to the control in the telescopic end of the zoom lens in the electronic zoom region. Therefore, the hand shake correcting function cannot be effectively utilized even at a position of a high electronic zoom magnification where the hand shake correction ability is high.